To flow liquids in pipes, energy must be expended to overcome frictional losses. This energy is extracted from the liquid pressure, which decreases along the pipe in the direction of flow. For a fixed pipe diameter, these pressure drops increase with increasing flow rate until a maximum is reached when the pressure drop along the pipe equals the supply pressure at the beginning of the pipe. When flow in the pipe is turbulent (flow Reynolds number=mean fluid velocity.times.pipe diameter.div.fluid kinematic viscosity greater than about 2000) this maximum flow rate can be increased by the addition of small amounts of certain high molecular weight linear polymers to the liquid. These polymers interact with the turbulent flow processes and reduce frictional pressure losses such that the pressure drop for a given flow rate is less, or the maximum flow rate for a given pressure drop is larger. This phenomenon is commonly called drag reduction. It has been used in commercial oil pipeline, fire hoses and storm sewers to increase the flow capacities of existing systems. It can also be used to reduce supply pressures, pumping costs, and/or pipe diameters for given flow capacities.
The instant invention discloses new efficient drag reduction agents in aqueous liquids which are a novel class of interpolymer complexes of acrylamide/metal styrene sulfonate and acrylamide/methacrylamidopropyltrimethylammonium chloride.
We note that high molecular weight polymeric materials in general, are considered useful as drag reduction agents when dissolved in an appropriate solvent system. For example, very high molecular weight water soluble polymers such as polyethylene oxide (PEO), polyacrylamide (PAM) and partially hydrolyzed polyacrylamide (HPAM) have been demonstrated to reduce drag in turbulent flow of aqueous liquid. The major reason for this reduction in fluid drag is due in large part to the very large dimensions of the individual polymer chain as compared to the dimension of the single solvent molecules. Any increase in size of the polymer chain will produce a corresponding enhancement in the drag reduction. This effect is maximized, when the polymer is dissolved in a "good" solvent. Therefore, in general, a hydrocarbon soluble polymer is useful in hydrocarbon solvents while a water soluble polymer is useful in aqueous systems. With regard to aqueous systems, polyelectrolytes are very useful and the most commonly used materials. However, it is generally quite difficult from a synthetic viewpoint to form a high or ultrahigh molecular weight water soluble polymer. This is due in part to both the presence of minutes amounts of impurities in the monomer feed which terminate the polymerization sequence and the very substantial shear sensitivity of these materials. Relatively small shear streeses are capable of causing severe deterioration in these high molecular weight polymers.
The instant invention discloses that interpolymer complexes, composed of an anionic copolymer and a cationic copolymer can be useful as drag reduction agents for aqueous solution systems, as an alternative to very high molecular weight polymers.
The anionic and cationic units need not be present in an aquimolar amount.
Typical water soluble monomers incorporated into the copolymers that are envisioned in the present invention are listed as follows:
Anionic: 2-acrylamido-2-methylpropane sulfonic acid, sodium styrene sulfonate, (meth)acrylic acid, 2-sulfoethylmethacrylate, and the like. PA0 Cationic: methacrylamidopropyltrimethylammonium chloride, dimethyldiallylammonium chloride, diethyldiallylammonium chloride, 2-methacryloxy-2-ethyltrimethylammonium chloride, trimethylmethacryloxyethylammonium methosulfate, 2-acrylamido-2-methylpropyltrimethylammonium chloride, vinylbenzyltrimethylammonium chloride, and the like. PA0 Nonionic: acrylamide, (N,N-dimethyl)acrylamide, hydroxyethyl(meth)acrylate, alkyl substituted acrylamides, (meth)acrylates, N-vinyllactones (e.g., n-vinyl-2pyrrolidone), and the like.
These monomers posses the appropriate water solubility for polymerization to take place.
The instant invention discloses that these interpolymer complexes can be usefuel as drag reduction agents for multicomponent aqueous solutions, e.g., well control and workover fluids, marine applications, blood and the like. In the latter fluid, addition of the interpolymer complex will enhance the blood flow rate through the circulation system of the living species through the circulation system of the living species (animal or homosapiens). In most instances, this would have a beneficial effect on the organism, such as enhancing the rate blood can carry oxygen, medicines, nutrients and the like to an organ. Similar enhancements would be observed with regard to fluid circulation in plants.